Piston converter for downhole drilling tool

ABSTRACT

A steerable drilling tool in accordance to an embodiment includes a steering actuator having an axially moveable piston connected to a steering pad by a linkage to convert axial movement of the piston into a radial movement of the steering pad.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 62/158,836, filed May 8, 2015, whichis incorporated herein by reference in its entirety.

BACKGROUND

This section provides background information to facilitate a betterunderstanding of the various aspects of the disclosure. It should beunderstood that the statements in this section of this document are tobe read in this light, and not as admissions of prior art.

Oil and gas reservoirs may be accessed by drilling wellbores to enableproduction of hydrocarbon fluid, e.g. oil and/or gas, to a surfacelocation. In many environments, directional drilling techniques havebeen employed to gain better access to the desired reservoirs by formingdeviated wellbores as opposed to traditional vertical wellbores.However, forming deviated wellbore sections can be difficult andrequires directional control over the orientation of the drill bit usedto drill the deviated wellbore.

Rotary steerable drilling systems have been used to drill deviatedwellbore sections while enabling control over the drilling directions.Such drilling systems often are classified as push-the-bit systems orpoint-the-bit systems and allow an operator to change the orientation ofthe drill bit and thus the direction of the wellbore.

SUMMARY

A steerable drilling tool in accordance to an embodiment includes asteering actuator having an axially moveable piston connected to asteering pad by a linkage to convert the axial movement of the pistoninto a radial movement of the steering pad.

A method includes deploying a bottom hole assembly (BHA) on a drillstring in a wellbore, the BHA including a drill bit and a steeringactuator having an axially moveable piston connected to a steering padby a linkage, axially moving the piston in response to the applicationof a hydraulic pressure, radially extending the steering pad in responseto the axially moving the piston and steering the drill bit in responseto radially extending the steering pad.

A drilling system includes a BHA deployed in a wellbore on a drillstring, the BHA including a drill bit and a steering actuator having anaxially moveable piston connected to a steering pad by a linkage toconvert the axial movement of the piston into a radial movement of thesteering pad.

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofclaimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with standard practice in the industry, variousfeatures may not be drawn to scale. In fact, the dimensions of variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an example of a drill string incorporatinga steerable drilling system and piston converter according to one ormore aspects of the disclosure.

FIG. 2 illustrates an example of a steerable drilling tool incorporatinga steering actuator piston converter according to one or more aspects ofthe disclosure.

FIG. 3 illustrates a point or hybrid type of steerable drilling toolincorporating an axial piston and piston converter according to one ormore aspects of the disclosure.

FIG. 4 illustrates a push type steerable drilling tool incorporating anaxial piston and piston converter according to one or more aspects ofthe disclosure.

FIG. 5 illustrates a prior art radial piston type of steering actuator.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the disclosure. These are, of course,merely examples and are not intended to be limiting. In addition, thedisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

As used herein, the terms connect, connection, connected, in connectionwith, and connecting may be used to mean in direct connection with or inconnection with via one or more elements. Similarly, the terms couple,coupling, coupled, coupled together, and coupled with may be used tomean directly coupled together or coupled together via one or moreelements. Terms such as up, down, top and bottom and other like termsindicating relative positions to a given point or element are may beutilized to more clearly describe some elements. Commonly, these termsrelate to a reference point such as the surface from which drillingoperations are initiated.

FIG. 1 illustrates a drilling system 20 in which piston converters 10for steerable systems can be incorporated. System 20 includes a bottomhole assembly (BHA) 22 which is part of a drill string 24 used to form adirectionally drilled wellbore 26. The illustrated bottom hole assembly22 of drilling system 20 includes a steerable drilling assembly 28, e.g.a rotary steerable system, which controls the drilling orientation of adrill bit 30. The steerable drilling assembly 28 in FIG. 1 isillustrated as a hybrid type system including steerable systemcomponents 32, 34 which pivot with respect to each other to enable thedesired directional drilling of wellbore 26. Steering actuators 36 maybe mounted between components 32 and 34 to control the pivoting ofcomponent 34 with respect to component 32 by providing the desiredlateral forces for steering the steerable drilling assembly 28 whenforming the desired, deviated wellbore 26. The steerable systemcomponents 32, 34 may be coupled together by a pivot joint 38, such as auniversal joint. The illustrated steerable drilling system is anon-limiting example of a steerable drilling system in which embodimentsof this disclosure can be incorporated.

The depicted steering actuators 36 incorporate a piston converter,generally denoted by the numeral 10, operationally connecting an axiallyaligned piston 12 to a radially moveable pad 14. The axial movement ofpiston 12 is transferred to the radial movement of pad 14. A controlsystem generally identified with the numeral 40 selectively directsdrilling fluid to the steering actuators 36 to extend the pads 14radially or laterally relative to the bottom hole assembly (e.g., too,drill string) and into contact with the outer steerable component 34(e.g., sleeve) or into contact with the wellbore wall to steer the drillbit 30. The control system 40 may include for example controlelectronics 42 and one or more valves 44 (e.g., spider valve, bistablevalve, etc.). The steering actuator can be provided in various forms.Non-limiting examples of steerable systems in which the piston convertcan be utilized are disclosed in U.S. Pat. Nos. 8,590,636, 8,701,795,8,708,064, 8,763,725 and 9,057,223, the teachings of which areincorporated herein by reference.

Depending on the environment and the operational parameters of thedrilling job, drilling system 20 may comprise a variety of otherfeatures. For example, drill string 24 may include drill collars 46which, in turn, may be designed to incorporate desired drilling modules,such as logging-while-drilling and/or measurement-while-drilling modules48. In some applications, stabilizers may be used along the drill stringto stabilize the drill string with respect to the surrounding wellborewall. Various surface systems also may form a part of the drillingsystem 20. In the example illustrated, a drilling rig 50 is positionedabove the wellbore 26 and a drilling mud system 52 is used incooperation with the drilling rig. For example, the drilling mud system52 may be positioned to deliver drilling fluid 54 from a drilling fluidtank 56. The drilling fluid 54 is pumped (pump 53) through appropriatetubing 58 and delivered down through drilling rig 50, into drill string24, and down through drill bit 30. In many applications, the return flowof drilling fluid flows back up to the surface through an annulus 60between the drill string 24 and the surrounding wellbore wall (seearrows 62 showing flow down through drill string 24 and up throughannulus 60). The drilling system 20 also may comprise a surface controlsystem 64 which may be used to communicate with steerable drillingassembly 28. In some embodiments, the surface control system 64communicates with a downhole steering control system within steerabledrilling assembly 28.

FIG. 2 schematically illustrates a non-liming example of a steerabledrilling assembly 28 incorporating a steering actuator 36 and pistonconverter 10 in accordance to an embodiment. With additional referenceto FIG. 1, the illustrated steerable drilling assembly 28 is in the formof a rotary steerable system which utilizes the steering actuators 36 tocontrol the relative angular orientation between steering components 32and 34. The steering components 32 and 34 are pivotally coupled to eachother via pivot joint 38 which, in this particular example, is in theform of a universal joint. Downhole drilling tools generally utilizedthe pumping pressure (pump 53), of the drilling fluid 54 to control thesteering actuator 36. The drilling fluid is directed for example by thedownhole steering control system 40, through a control valve 44 to thepiston 14 of the steering actuator 36 to drive the piston 12 axiallyrelative to the axis 66 which in turn radially extends the pad 14outward relative to the longitudinal axis 66 of the tool (e.g., BHA). Inaccordance to embodiments, the piston converter 10 is a mechanical link.In the example of FIG. 2, the pad 14 extends radially outward to apply asteering force and pivot the steering components 32, 34 relative to oneanother. In some steerable tools the pads are extended radially from thedrilling tool to contact and apply the steering force to the wall ofborehole.

FIGS. 3 and 4 are schematic illustrations of steerable drilling tools 28incorporating steering actuators 36 utilizing a piston converter 10 inaccordance to one or more aspects of the disclosure. The piston 12 ismoveably disposed in a longitudinally extending cylinder 68, i.e., alongthe longitudinal axis 66 of the tool, as opposed to being oriented inthe radial direction. Piston converter 10 is a mechanical linkage thattransfers the axial movement of the piston 14 into a radial movement ofthe pad 14.

The piston cylinder 68 is oriented in the axial direction with thepiston 12 movement and the piston push in the axial direction inresponse to the application of hydraulic fluid 54, e.g. drilling mud.The piston cylinder 68 is longer and the movement of piston 12 is longerthan that permitted in a radial piston arrangement, see e.g., U.S. Pat.No. 8,590,636. The longer axial movement allows for more liftingmovement of the rocker assembly 70 (see, FIG. 4) and the pad 14. Duringoperation the pad (e.g., the top surface) or other components wearand/or become washed out requiring that the pad assembly move furtherradially than prior to the wear. The axial piston facilitates theadditional radial movement without compromising the piston seal 72, e.g.the piston seal pushed out of the pressure chamber. The circular shapedseal 72 (e.g., O-ring) circumferentially encircling the axially movingpiston 12 is a reliable seal. FIG. 3 illustrates the piston converterarranged in a point-type or hybrid-type steerable tool and FIG. 4illustrates the piston converter arranged steering actuator in apush-the-bit steerable drilling tool.

FIG. 5 illustrates an example of a prior art steering actuator abledrilling tool and prior art radial piston assembly. A furtherdescription of a prior art radial piston assembly is disclosed in U.S.Pat. No. 8,590,636, the teachings of which are incorporated herein byreference. Hydraulic pressure, e.g., the drilling mud 54, acts on theactuator piston 12 causing it to move radially relative to thelongitudinal axis 66 of the steerable drilling tool as it pivots aboutthe hinge pin 74. Because of the space restriction in the radialdirection, the opening angle 76 of the hinged piston may be limited toaround six degrees. Space is restricted, or limited, in the radialdirection according to the drilling tool size. During drillingoperations the piston rocker top surface 70 and other components maywear, permitting the piston to open greater than the original limit.When this happens, the dynamic piston seal 78 may pop out of the metalpocket and the sealing mechanism may be damaged. This could result inwashout of the piston and reduction in the steering performance of thedrilling tool.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the disclosure.Those skilled in the art should appreciate that they may readily use thedisclosure as a basis for designing or modifying other processes andstructures for carrying out the same purposes and/or achieving the sameadvantages of the embodiments introduced herein. Additionally, it shouldbe understood that references to “one embodiment” or “an embodiment” ofthe present disclosure are not intended to be interpreted as excludingthe existence of additional embodiments that also incorporate therecited features. For example, features shown in individual embodimentsreferred to above may be used together in combinations other than thosewhich have been shown and described specifically. Accordingly, any suchmodification is intended to be included within the scope of thisdisclosure. In the claims, means-plus-function clauses are intended tocover the structures described herein as performing the recited functionand not just structural equivalents, but also equivalent structures.Thus, although a nail and a screw may not be structural equivalents inthat a nail employs a cylindrical surface to secure wooden partstogether, whereas a screw employs a helical surface, in the environmentof fastening wooden parts, a nail and a screw may be equivalentstructures. It is the express intention of the applicant not to invokemeans-plus-function for any limitations of any of the claims herein,except for those in which the claim expressly uses the words ‘means for’together with an associated function.

What is claimed is:
 1. A steerable drilling tool, comprising a steeringactuator having an axially moveable piston connected to a steering padby a linkage to convert axial movement of the piston into a radialmovement of the steering pad.
 2. The tool of claim 1, wherein thesteering pad comprises a rocker assembly.
 3. The tool of claim 1,comprising a seal circumferentially encircling the axially moveablepiston.
 4. The tool of claim 1, wherein the steering pad comprises arocker assembly and further comprising a seal circumferentiallyencircling the axially moveable piston.
 5. The tool of claim 1, furthercomprising a pair of steering components pivotally mounted to each othervia a pivot joint and extending axially along a tool axis; and thesteering actuator disposed with one of the pair of steering componentssuch that axial movement of the piston moves the steering pad radiallyrelative to the tool axis thereby pivoting the steering componentsrelative to one another.
 6. The tool of claim 5, wherein the steeringpad comprises a rocker assembly.
 7. The tool of claim 5, comprising aseal circumferentially encircling the axially moveable piston.
 8. Thetool of claim 5, wherein the steering pad comprises a rocker assemblyand further comprising a seal circumferentially encircling the axiallymoveable piston.
 9. A method, comprising: deploying a bottom holeassembly (BHA) on a drill string in a wellbore, the BHA comprising adrill bit and a steering actuator comprising an axially moveable pistonconnected to a steering pad by a linkage; axially moving the piston inresponse to the application of a hydraulic pressure; radially extendingthe steering pad in response to the axially moving the piston; andsteering the drill bit in response to radially extending the steeringpad.
 10. The method of claim 9, wherein the steering pad comprises arocker assembly.
 11. The method of claim 9, comprising a sealcircumferentially encircling the axially moveable piston.
 12. The methodof claim 9, wherein the steering pad comprises a rocker assembly andfurther comprising a seal circumferentially encircling the axiallymoveable piston.
 13. The method of claim 9, wherein the radiallyextending the steering pad comprises contacting the wellbore with thesteering pad.
 14. The method of claim 9, wherein the radially extendingthe steering pad comprises pivoting a first and a second steeringcomponent relative to one another.
 15. The method of claim 14,comprising a seal circumferentially encircling the axially moveablepiston.
 16. A drilling system, comprising a bottom hole assembly (BHA)deployed in a wellbore on a drill string, the BHA comprising a drill bitand a steering actuator having an axially moveable piston connected to asteering pad by a linkage to convert axial movement of the piston into aradial movement of the steering pad.
 17. The system of claim 16,comprising a seal circumferentially encircling the axially moveablepiston.
 18. The system of claim 16, wherein the steering pad comprises arocker assembly and further comprising a seal circumferentiallyencircling the axially moveable piston.
 19. The system of claim 16,wherein the BHA comprises a pair of steering components pivotallymounted to each other via a pivot joint and extending axially along atool axis, whereby the steering components are pivoted relative to oneanother in response to radially extending the steering pad.
 20. Thesystem of claim 19, comprising a seal circumferentially encircling theaxially moveable piston.